Kamen Rider OOO (仮面ライダーオーズ／ＯＯＯ, Kamen Raidā Ōzu) is the twelfth series in the Heisei period run of the Kamen Rider Series, and the twenty-first overall. It began airing on September 5, 2010, the week following the conclusion of Kamen Rider W, joining Tensou Sentai Goseiger in the Super Hero Time lineup.